1982 280GE LWB W460 RHD

The headlights do not work

- no low beam, no high beam
- high beam flasher works so it's not the bulbs or the headlight housing
- parking lights inside the headlight work

Using the colour-coded wire diagram attached, I traced wires and tested them both with a multi-function meter and a light on/off tool. Here's what I found so far:

Fuse Box - no power to 3-4-5-6 (hot side)
Check fuses: Hot (bottom) side of 3-4-5-6 fuses - no power
-> Jumping them with an alligator clip turned the headlights on, but started smoking the wire.
=>Unsure if this was due to thinness or if I was about to damage something.
-> This means the headlights work, and the break is somewhere upstream of fuse box

Headlight Switch - Works

Check the headlight switch
2.5 red wire inbound from alternator 12v - The inbound power is working
2.5 white and black wire outbound with switch on - 12 v - The outbound power is working
Bypassing headlight switch makes no difference, conclude switch is working and not the problem

Multifunction turn signal stalk and cable - No power (but other functions work)

2.5 white and black (looks similar to powered wire at headlight toggle switch - no power
2.5 yellow and 2.5 white at the plug that connects the multi-switch turn signal - no power
This suggests the 2.5 white and thin black wire outbound from the headlight switch is not getting 12v to the multifunction stalk cable. If the white & black cable inbound is the source of power from the headlight, then it must be broken somewhere. There is a connector between such a wire within the dashboard, and this too had no power male or female sides.

However, I do not know if the white/black wire is the one that is supposed to power the yellow and white wires that go to the fuse box and then to the headlights. Unfortunately even with the steering wheel and lower dashboard removed and the fuse box out, I cannot trace the wire from the headlight switch to see where it goes. And logically, it seems unlikely that a wire inside the dash inside the car inside the garage would fail (no evidence of mice). It would be more likely to be a switch or relay, but testing so far does not point to the obvious.

Question: Any idea what's wrong?

Question: Does anyone have a detailed schematic of the multifunction stalk and cable wiring and the connections between it and the headlight switch?

Shade-tree mechanic question: If I cannot find the source of the break, what can I bypass with a new 2.5 wire so the headlights turn on, switch from high to low and optionally flash on?